The present invention relates to a straightening device for the wire of a wire electroerosion machine with a block, to which is fitted at least one contact point for the wire and with contracting means for the wire located in the contact point.
In a known machine of this type, there are two contact points in the form of plates. One of these plates is located at the top of the block and the other is located at the bottom of the block. The plates are spaced by a distance of approximately 100 mm. The machine wire runs in a vertical direction, the wire guide being constructed in such a way that the upper and lower portions of the wire can be moved independently of one another in one plane to which the eroding wire is substantially at right angles. This arrangement makes it possible to vertically adjust the eroding wire, or to bring it into any desired sloping position.
If a cut is to be made in the workpiece at a specific angle, then the block is initially brought into a position such that the plane, in which the surface of the contact points is located, forms the desired angle with the perpendicular. Using a guide means for the wire, the latter is then moved until it is in contact with the contact points. When the wire contacts the particular contact point, the latter supplies a pulse to the central processing unit of the machine. If the machine central processing unit receives the pulse from the upper and lower contact points simultaneously, the central processing unit evaluates the pulse in such a way that the wire is parallel to or in the plane in which the surfaces of the contact points are also located. The wire has the desired slope and the machining operation can commence.
If the pulses are successively emitted by the contact points, then the central processing unit investigates which of the two pulses has arrived earlier than the other. There is then caused a corresponding displacement of the upper or lower wire portion and consequently a change in the wire slope. The wire is now moved once again up to the contact points and the synchronism of the pulses supplied by the contact points is again checked. This step is either followed by a further wire position correction process in the manner described hereinbefore, or it is indicated that the eroding wire has the desired position.
The contact point of the known device contains a plate having a substantially rectangular groove and the plate portion having this groove projects from the block. The machine wire can be inserted in the groove. The plate groove sides, which are at right angles to one another, are provided with contacting means that are insulated from the remainder of the plate which is made from metal. The contacting means are constituted by electrically conductive platelets, which are fitted in an insulated manner to the sides of the groove and whose free surface is vertical.
It was not possible, with a wire electroerosion machine constructed in this way, to adjust the wire position with a precision in the range of 2 to 3 thousandths mm. Thus, if the wire is brought up to the platelets, the edges of the latter decisively influence the time of supplying the pulse to the central processing unit. This influence is not a linear quantity, because a decisive part is played in this connection by any dirtying of the edge of the platelet or the like, apart from the slope of wire with respect to the platelets.